Thin Wafer Handling

Download SUSS MicroTec technical publications, white papers and application notes about thin wafer handling.

Introduction of a unified equipment platform for UV initiated processes in conjunction with the application of electrostatic carriers as thin wafer handling solution

This paper introduces the MA8 Gen3 Aligner generation designed specifically for the development of 3D and MEMS packaging technologies. Photolithography on the wafer backside, wafer bonding and replication of microstructures are specific 3D / MEMS processes. They have in common that all of them require precision alignment and often will have to run on ultra-thin wafers. The MA8 Gen3 allows to run all the processes above on a unified equipment platform and therefore offers the ideal equipment solution for 3D and MEMS technologies.

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Polyimide based Temporary Wafer Bonding Technology for High Temperature Compliant TSV Backside Processing and Thin Device Handling

Temporary wafer bonding for thin wafer processing is one of the key technologies of 3D system integration. In this
context we introduce the polyimide material HD3007, which is suitable for temporary bonding of silicon wafers to carrier wafers by using a thermo compression process. Coating and bonding processes for 200 mm and 150mm wafers with and without topography as well as two de-bonding concepts which are based on laser assisted and solvent assisted release processes are presented.

Based on tests with temporary bonded 200 mm wafers we found a very high compatibility of the bonded compound wafers with standard WLP process equipment and work flows suitable for backside processing of “via first” TSV wafers. Processes like silicon back grinding to a remaining thickness of 60 μm, dry etching, wet etching, CMP, PVD, spin coating of resists and polymers, lithography, electro plating and polymer curing were evaluated and are described in detail. Even at high temperatures up to 300 °C and vacuum levels up to 10-4 mbar, the temporary bond layer was stable and no delamination occurred. 60 μm thin wafers could be processed and de-bonded without any problems using both release methods. De-bonding times of less than a couple minutes can be realized with laser assisted debonding and several minutes with a solvent based release. Compared to glues of other temporary handling systems, the proposed material offers the highest temperature budget for thin wafer backside processing as well as fast and easy de-bonding at room temperature.

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Thin Wafer Handling – Study of Temporary Wafer Bonding Materials and Processes

This paper reviews the major adhesives and processes used for 3D TSV thin wafer handling, provides thermal and other performance data on the materials and processes and attempts to establish a first order estimate of process related thermal performance using a common analytical method.

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Thin Wafer Handling Challenges and Emerging Solutions

Temporary bonding attaches substrates to a carrier so that after thinning to the desired thickness further backside fabrications steps can be conducted with “normal” process flows in standard semiconductor equipment. The selection of a suitable temporary adhesive is key to the success of thin wafer handling. The major requirements of temporary adhesives are related to its process flow, thermal stability, chemical resistance, and mechanical strength. The ideal thermal stability should allow high temperature processing up to 400C for dielectric deposition in high aspect ratio vias, polymer curing, solder reflow, metal sintering, permanent bonding or other high temperature processing. The adhesive must be resistant to the chemicals commonly used after wafer thinning. Mechanical strength is required to hold the thin wafer rigidly during processing, especially during permanent bonding applications otherwise the thinned wafer will flex and prevent bonding. The challenge arises in finding a simultaneous solution to these problems while allowing for the gentle release of the thinned substrate to its final, permanent substrate or package without yield loss or stress. This paper will highlight some of the more recent solutions for thin wafer handling that have emerged through technology innovation.

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